The invention relates to a device for determining a quantity of consumable product contained in at least one reservoir, of the type comprising a capacitive arrangement having a conductive plate associated with such a reservoir, for instance having such a plate normally pressed against a wall of such a reservoir, in order to produce a signal representing the quantity of product contained in the said reservoir.
The invention also concerns an improvement facilitating the fitting of the reservoir in spite of the presence of such a conductive plate, whilst increasing the useful surface of the latter (and consequently the capacitance of the capacitor thus formed), all other things being equal.
The invention also concerns a document printing device having a chassis and a carriage compelled to move along guidance means on this chassis and in which the said carriage carries at least one removable printing product reservoir and a conductive plate able to constitute a capacitor in association with the reservoir in question, the printing device having means of determining the quantity of printing product contained in the reservoir, provided with the improvement mentioned above.
A conventional printing device has one or more reservoirs and a corresponding number of print heads, mounted on a carriage compelled to move along guidance means arranged on a chassis. The printer is completed by a mechanism for moving a printing medium (the sheet of paper), also arranged on the chassis. The said printing medium is moved perpendicularly to the path of the carriage. The latter has a support on which the reservoir or reservoirs are mounted, these being removable individually or in a group or groups. Thus, on an improved printer, there may be up to five reservoirs. Three reservoirs are filled with printing products for the three primary colours: cyan, magenta and yellow, a fourth reservoir is filled with black printing product and a fifth can be provided for containing a colourless product sprayed onto the paper in order to optimise the conditions of application of the pigmented products.
Several reservoirs can be grouped together in a cartridge, for example grouping together the three primary colours, or on the other hand be independent of each other in order to be able to be changed individually. Each reservoir or group of reservoirs is therefore removably mounted on the carriage support. The corresponding print head or heads can be integral with the reservoir or reservoirs (in which case they are changed at the same time as the reservoir or cartridge). In other cases, the print head or heads are mounted permanently on the carriage.
Several ways are known for detecting a printing product level in a reservoir of such a printing device. Notably, it is known that there can be associated with the reservoir a capacitive arrangement placed in a resonant circuit to which an excitation signal is applied, generally a high-frequency alternating signal. The signal transmitted by such a capacitive arrangement varies according to the quantity of ink remaining in the reservoir. This variation can therefore be used for indicating to the user the degree to which the reservoir is filled or at least the fact that a minimum level has been reached. According to the information collected, the user can replace the reservoir or change a cartridge containing this reservoir. Where the carriage carries several reservoirs, the capacitive arrangement designated above comprises several capacitors each surrounding one of the reservoirs.
The document EP 0 028 399 describes a system of this type in which the capacitor is formed by two metal plates between which the ink reservoir is situated. A resonant oscillating circuit is calibrated so that its resonant frequency is reached when the ink level has dropped to a predetermined value.
Several solutions have also been experimented with in order to connect the elements of the device which are on the carriage to those which are on the fixed chassis. For example, a resonant circuit can be mounted on the carriage, the capacitor of this circuit including the reservoir. One resonant circuit per reservoir can be established and an analogue switch can be used for successively making the measurements corresponding to the different reservoirs. Such a system is relatively expensive if it is necessary to provide one resonant circuit per reservoir. The use of an analogue switch also creates stray capacitances which substantially interfere with the measurements.
If the resonant circuit is placed on the chassis, the signals must then be conveyed by flexible cables connecting the carriage and the chassis. These cables create problems of electromagnetic compatibility due to the conveyance of high-frequency signals, and stray capacitances and inductances are also created between the cables, which also interfere with the measurements.
Moreover, if the measurement circuits are placed on the carriage, the latter can be the origin of electrostatic discharges.
Furthermore, in such a system, it is clear that the reservoir or reservoirs must be mounted removably on the carriage and that at least one conductive plate, forming part of the aforementioned capacitive arrangement, must also be carried by the carriage. Since it is a case of measuring a level of liquid product contained in the reservoir, the said plate must be pressed against a normally vertical face of the reservoir. Thus, considering FIGS. 1 and 2, which illustrate the state of the art, FIG. 1 depicts a reservoir A on the point of being mounted on a support B on the carriage. FIG. 2 shows the reservoir installed on this support. A comparison of the two figures shows that it is necessary to incline the reservoir in order to fit it (FIG. 1), which makes it necessary to provide an end wall with an inclined part D. In the end, only the lower part of the corresponding face of the reservoir is in contact with the lower part of the said end wall C. However, it is advantageous, for various technical reasons which will emerge later, to arrange the said conductive plate against the end face E of the reservoir. It will be understood under these circumstances that the surface of the conductive plate would be limited in order to concern, from the electrical point of view, only the lower part of the reservoir in order not to interfere with the fitting of the latter. The capacitance of the capacitor which would be available for making the measurement would be relatively limited.
The invention makes it possible to overcome all these drawbacks.
One important idea of the invention consists of arranging electrical connection means between the chassis and the carriage in order to electrically bring into service a capacitor plate associated with a reservoir when the said carriage occupies a predetermined position. If the carriage carries several reservoirs, several corresponding predetermined positions are thus defined, for which the level measurements can be made individually and successively for the different reservoirs.
More precisely, the invention concerns a device for determining a quantity of consumable product contained in at least one reservoir, of the type comprising the following components: a capacitive arrangement including a conductive plate associated with the said reservoir, excitation signal production means able to be connected to the said capacitive arrangement, and detection and measurement means for detecting and processing a resulting signal transmitted by the said capacitive arrangement and representing a quantity of product contained in the said reservoir, characterised in that, some of the components mentioned above being mounted on a chassis and others being fixed to a movable carriage moving along a guidance means on the said chassis, electrical connection means are arranged between the said chassis and the said carriage in order to electrically bring into service the said plate corresponding to the said reservoir, for a predetermined position of the said carriage.
Preferably, the capacitive arrangement is associated with an inductor and a resistor, in order to form a resonant circuit.
Where several reservoirs are used, the invention also concerns a device as defined above characterised in that it has several reservoirs grouped side by side, in that the said capacitive arrangement includes several conductive plates associated respectively with the said reservoirs and in that the said connection means form an electrical selector for electrically selecting and bringing into service the aforementioned plates corresponding respectively to the said reservoirs, for predetermined positions of the said carriage.
According to a preferred embodiment, the connection means forming an electrical selector comprise on the one hand a common contact element connected to the said excitation signal production means and on the other hand a plurality of contact elements respectively connected to conductive plates associated with the said reservoirs.
According to another improvement, the electrical connection means are designed so as to make it possible to detect the absence of one or more reservoirs on the carriage. In this case, each contact element of the plurality of contact elements mentioned above has an elastically flexible blade forming a loop. One end of this loop enters, in the unstressed state of the said blade, a recess reserved for the corresponding reservoir and is out of contact with the said common contact element in any position of the said carriage. On the other hand, when the said reservoir is placed in its recess, pushing the said end, the stressed loop is deformed, so that part of it can come into contact with the aforementioned common contact element, for a corresponding predetermined position of the said carriage.
The invention also concerns a document printing device having a chassis, a carriage compelled to move along guidance means arranged on the said chassis and a mechanism for moving a printing medium arranged on the said chassis, in which the said carriage carries at least one printing product reservoir and a print head connected to the said reservoir, the latter being removable and mounted on a corresponding support on the said carriage, of the type also having means of determining the quantity of ink contained in the said reservoir, comprising the following components: a capacitive arrangement including at least one conductive plate associated with the said reservoir, means of producing an excitation signal, able to be connected to the said capacitive arrangement, and detection and measurement means for detecting and processing a resulting signal transmitted by the said capacitive arrangement and representing a quantity of printing product contained in the said reservoir, characterised in that, some of the components mentioned being mounted on the said chassis and others being mounted on the said carriage, electrical connection means are arranged between the said chassis and the said carriage in order to electrically put into service the said plate corresponding to the said reservoir, for a predetermined position of the said carriage.
Where the printing device has several reservoirs, these are grouped together side by side on the support on the said carriage, and the said capacitive arrangement includes several conductive plates associated respectively with the said reservoirs. The said connection means form an electrical selector for electrically selecting and putting into service the aforementioned plates corresponding respectively to the said reservoirs, for predetermined positions of the said carriage.
The invention also proposes an arrangement which affords an easy fitting of the reservoir, good contact between the conductive plate and the face of the reservoir against which it is to be applied, and an increased surface area of this plate, all other things being equal.
To this end, the invention concerns a device for determining the quantity of consumable product contained in at least one removable reservoir able to be mounted on a support, of the type comprising the following components: a capacitive arrangement including at least one conductive plate associated with the said reservoir, means of producing an excitation signal which are able to be connected to the said capacitive arrangement, and detection and measurement means for detecting and processing a resulting signal transmitted by the said capacitive arrangement and representing a quantity of product contained in a corresponding reservoir, some of the said components being mounted on a chassis and others being mounted on a movable carriage moving along a guidance means on the said chassis, characterised in that the said support has a movable block carrying the said plate, in that this block, in the absence of any force, occupies a leaving-clear position facilitating the insertion of the said reservoir and in that it is arranged to be moved by the fitting of the said reservoir and to be maintained in another position when the reservoir is mounted on the said support, the said plate being applied against a face of the said reservoir when the said block is maintained in this other position.
The device defined above can also be characterised in that the said movable block carries an elastic electrical contact element, electrically connected to the said plate and able to occupy two positions, a service position when the said reservoir is in contact with the said movable block and an idle position when the said reservoir is not mounted on its support, the said contact element being able, when it is in the said service position, to cooperate with another electrical contact element for at least one predetermined position of the said carriage in order to establish an electrical connection between the aforementioned two parts of the said components.
Where the support is arranged to carry several reservoirs at predetermined locations, an aforementioned movable block carrying a plate is arranged at each of its locations in order for it to be able to cooperate with the corresponding reservoir.
In this case, the device is also characterised in that the said contact elements associated respectively with the reservoirs are similar and offset along one side of the said carriage parallel to its direction of movement, and in that the said other contact element (or common contact element) is mounted at a fixed location on the said chassis and is capable of cooperating with each of the contact elements for respective predetermined positions of the said carriage, the said contact elements defining selection means forming an electrical selector, arranged between the said chassis and the said carriage in order to electrically select and put into service the aforementioned plates corresponding respectively to the said reservoirs, for the said predetermined positions of the said carriage.
This arrangement also makes it possible to detect the absence of a reservoir on the carriage. This is because each contact element associated with a plate can have an elastically flexible blade, for example metallic, attached to an aforementioned movable block. When a reservoir is placed on the support and the corresponding movable block is in contact therewith, part of this blade is placed so that it can come into contact with the said other contact element for a corresponding predetermined position of the said carriage. On the other hand, the said blade is out of contact with the said other contact element or common contact element, for any position of the carriage when the corresponding reservoir is not placed on the support.
In a particularly simple embodiment, the movable block or blocks are mounted so as to be hinged and tend to tilt freely towards a position placing the contact element in the aforementioned idle position.
The invention also concerns a document printing device having a chassis, a mechanism for moving the printing medium arranged on this chassis, and a carriage compelled to move along guidance means arranged on the said chassis, the said carriage carrying at least one print head and a support for at least one removable printing product reservoir, of the type also having means of determining the quantity of ink contained in the said reservoir, comprising the following components a capacitive arrangement including at least one conductive plate associated with the said reservoir, means of producing an excitation signal which are able to be connected to the said capacitive arrangement, and detection and measurement means for detecting and processing a resulting signal transmitted by the said capacitive arrangement and representing a quantity of printing product contained in the said reservoir, some of the said components being mounted on the said chassis and others being mounted on the said carriage, characterised in that the said support has a movable block carrying the said plate, in that this block, in the absence of any force, occupies a leaving-clear position facilitating the insertion of the said reservoir and in that it is arranged to be moved by the fitting of the said reservoir and to be maintained in another position when the reservoir is mounted on the said support, the said plate being applied against a face of the said reservoir when the said block is maintained in this other position.
The capacitive arrangement can form part of a resonant circuit.